1. Field of the Invention
This invention relates to a buffing apparatus, and more particularly to a buffing apparatus suitable to buff a thin plate work.
2. Description of the Related Art
In recent years, an increase in density of thin wires on a printed circuit board and an increase in number of layers of thin plates are demanded in accordance with a demand for miniaturization and increase in performance of various electronic apparatus. Consequently, reduction in thickness of thin plates as inner layer materials has proceeded, and polishing of such thin plate inner layer materials is required as a surface treatment to remove rust, soil and so forth of inner layer materials. However, the reduction in thickness of thin plates of inner layer materials to be polished so proceeds that, when a thin plate inner layer material is buffed using a buffing apparatus which is used popularly, the inner layer material is subjected to buckling by an extruding force of a buffing roll, resulting in failure in buffing. Therefore, it is demanded to develop a buffing apparatus suitable to buff a thin plate.
An exemplary one of conventional buffing apparatus will be described below with reference to FIGS. 1 to 4.
Referring first to FIGS. 1 and 2, an elongated buffing roll 2 is secured to a shaft 3 which is driven to rotate, and a backup roll 4 is disposed in an opposing relationship to the buffing roll 2. The buffing roll 2 includes an annular core 7 and an annular buff 2a secured to the annular core 7. Referring particularly to FIG. 2A, reference numeral 8 denotes a space. Pinch rolls 6 are each biased by an air cylinder or a like element into contact with a feed roll 5 which is driven to rotate.
A conventional fixing structure for the buffing roll will be described below with reference to FIGS. 3 and 4. The shaft 3 has a pair of threaded portions 3a formed at predetermined locations at the opposite end portions thereof, and the buffing roll 2 is secured to a predetermined location of the shaft 3 by fitting the elongated buffing roll 2 onto the shaft 3, inserting a pair of spacer collars 10 into the buffing roll 2 from the opposite ends of the buffing roll 2 and tightening a pair of threaded rings 11 to the threaded portions 3a of the shaft 3.
While a plate work is fed by the roll pairs each including the feed roll 5 and the pinch roll 6 with the lower face thereof held by the backup roll 4, the buffing roll 6 is rotated at the speed of about 2,000 to 3,000 rpm to buff the upper face of the plate work.
However, since the conventional buffing apparatus adopts the elongated buffing roll 2, it has a problem in that, when the thin plate member 9 is buffed, as the rear end of the plate member 9 passes the buffing roll 2, it is subjected to buckling by the force of the buffing roll 2 so that it is bent or curved. Buffing of a thin plate less than 0.2 mm thick is impossible with the conventional buffing apparatus which adopts such elongated buffing roll 2.
Further, in conventional buffing apparatus, since the feeding mechanism for a buff shaft is of a one-stage slide type which employs a motor as a power source and adaptation to the thickness of a work and control of the polishing pressure are performed by the single motor, there is a problem in that accurate pressure adjustment cannot be achieved.
Furthermore, since conventional buffing apparatus does not employ the method of measuring the diameter of the buffing roll to control the origin or the starting point but employs a positioning system wherein the point of time when the buffing roll is contacted with the hackup roll is set to the origin, each time a work having a different thickness is supplied, setting of the origin must be performed, and accordingly, it is impossible to successively supply works having different thicknesses.